Electronic mail or email is a store and forward method of composing, sending, storing, and receiving messages over electronic communication systems. Email tracking is directed to techniques for monitoring email delivery to an intended recipient. Email traditionally provides no mechanism for tracking a sent message. The system(s) involved will generally make an effort to either deliver mail or return a failure notice (“bounce message”), but there is no guarantee that a message will actually be delivered, let alone read by the recipient. This is in contrast to the postal mail system, which offers registered mail or other forms of tracking and tracing.
Most email tracking technologies use some form of digitally time-stamped record to reveal the exact time and date that an email was opened, along with the Internet protocol (IP) address of the recipient.
A web bug or web beacon is an object that is embedded in an email and is usually invisible to the recipient but allows checking that a recipient has viewed the email, and thus provides a form of email tracking. When the recipient reads the email, the email client requests the image, letting the sender know that the email address is valid and that the email was viewed. However, tracking via web bugs can be prevented by using email clients that do not download images whose uniform resource locators (URLs) are embedded in hypertext markup language (HTML) emails. Many graphical email clients can be configured to avoid accessing remote images. Many modern email readers and email services will not load images when opening an HTML email from an unknown sender or that is suspected to be spam mail. The user must explicitly choose to load images. Web bugs can also be filtered out at the server level so that they never reach the recipient. As a result of these measures, web bugs have lost their effectiveness and cannot be relied on for email tracking. It is thus difficult to confirm electronic delivery or verification of an electronic communication such as an email with high reliability.